Process for producing oils with low pour points



May 9, 1944. 2,348,459

` PROCESS FOR PRODUCING OILS WITH LOW POUR POINTS B.` ENGEL Filed Dec.51. 193s Y mf fm Mm W4 r 5,.

M f W4 Patented May 9, 1944 PROCESS FOR PRoDUoING oiLs wrrn Low POURPoms Bruno Engel, Appelviken, Sweden, assigner to AktiebolagetSeparator-Nobel, Stockholm, Sweden, a corporation of Sweden ApplicationDecember 31, 1938, Serial No. 248,874

In Germany January 4, 1938 s claims. (ci. 19e-1s) In the dewaxing ofoils and tars as Well as their distillation and transformation productsit is generally desirable that the dewaxed oil should have as low a pourpoint and as nat a temperature-viscosity curve as possible. In order toremove the wax from the said products, they are diluted by addingagreater or lesser amount of a solvent and are then chilled,y whereuponthe solid wax precipitated at the low temperature is removed by means offilters, presses, centrifuges or the like.

In such processes the refrigerating energy required for the chilling isof great economic importance. It is therefore desirable to use as smallon amount as possible of such solvents by which is obtained an oil whosepour point is scarcely higher than the dewaxing temperature. Thisrequirement'is fullled only by solvents of the type which have a markedselectivity relative to the groups of hydrocarbons contained in theoils, such as parafnic and naphthenic and aro.- matic compounds."

The greater the selectivity of the solvent, the higher the temperaturewhich may be used for the removal of a given amount of solid wax and forobtaining a given pour point. On the other hand, if a solvent withoutselective effect is used, the dewaxing must be effected at acomparatively A low temperature if the same pour point is to be secured.

For instance, to produce an oil having a pour point of 15 C; from aRoumanian mineral oil` distillate by means of dewaxing, it is necessaryto cool to at least 40"C, if non-selective solvents,

such as propane, butane or naphtha, are used, f

whilea-'temperatureof only 15 to 17 C.l is suiiicient if a selectivesolvent, such as dichlorethane, is used. In the latter case the amountof solvent required is also substantially smaller than in the former. v

If paran base oils are treated, the selective qualities of the solventshave, of course, prac-V tically no disadvantageous effect on theviscositytemperature curve. But with mixed base oils, and to a stillhighervdegree with asphalt base oils, the

selectivity may cause disadvantages, as the highly polymerichydrocarbons, such as resins, asphalts, etc., are precipitated in moreor less colloidal form and make the removal of the wax more diiicult,the yield thereby often being considerably reduced. In order to avoidthis, aromatic hydrocarbons, such as benzene, toluene, are in many casesadded as so-called oil-dissolving agents to the ordinary dewaxingagents.

As a further disadvantageous phenomenon, it

may be mentioned that besides the solid waxprecipitated at the giventemperature, valuable parafnous hydrocarbons, which are liquid atordinary temperature, are precipitated orenclosed in the solid phase,which entails not only areduction in yield of oil but also a veryconsiderable reduction of the viscosityrindex of the dewaxed oil.

This phenomenon, which is particularly conspicuous in connection withmixed base oils, may make it impossible to obtain a given low pour pointwith the aid of selective dewaxing gents. If, for instance, it isdesirable to obtain a 4pour point of 20 C., it would be necessary totreat the oil with a suitable wax precipitating agent at a temperaturebetween 15 and 20 C. Within this temperature range and with the kindsofoils mentioned above, the selectivity is so high that a considerableproportion of the valuable parafiincus lubricatingoil constituents areenclosed in the precipitated solid wax, with a resultant reduction notonlyin yield but'also in the viscosity index. If, on the other hand, thedewaxing is carried out' at a comparatively high temperature, forinstance above 15 C., the solubility of the crystalline wax is too high,and the oils obtained have a pour point considerably higher than thatrequired. I

It has now been found that these objections can be avoidedby eifectingthe dewaxing with the aid of selective wax precipitating agents in twoor more stages. AA selective separation 'of the solid and fluid Waxparticles from the other groups of hydrocarbons is rst effected. ThenV aseparation at higher temperature of the mixture of wax hydrocarbons intosolid crystalline wax and uid lubricating 'oil" particles is'eiecte'd.Finally, the uid parainic hydrocarbons obtained in the second separationare, allor partly, kadded to the primary oil (hereinafter called ex--tract) obtained in the rst separation.

By this process `thel following advantages are obtained:

1. Only the solid hydrocarbons, which increase the pour point of theoil, are separated as the nal wax product. They are obtainedin very pureform.

2. By adding the uid Wax hydrocarbons to the primary oil, not onlylubricating oils with a paraffinic pour point, but also lubricants witha dat viscosity-temperature curve, are obtained.

3. It is allowable to keep in solution or to bring into solution arelatively great proportion of the soft wax, possibly allthe softwaxes', which, as is Well known, substantially raise the viscosity ndex,without substantially point.

If the first separating stage is carried out at a comparatively lowtemperature, the obtained extract is a concentrate of viscosity bearersrich in aromatics, which renders diicult the precipitation of. soft wax,etc., in the same manner as takes place on addition of so-called pourpoint reducers. Consequently the second separating stage, that is, thedivision into solid wax and par-v alinic lubricating oil components, canbe carried out at comparatively high temperatures. By mixing the extractfrom the rst stage with the fluid hydrocarbons liberated from the hardwax, the pour point of the hydrocarbons is substantially lowered, andsimultaneously the viscosity index of the dewaxed primary oil or extractand the total yield of oil are considerably raised.

This process is advantageously carried out in continuous operation incentrifuges, as indicated in the following example.

100 kg. of a Roumanian heavy distillate are mixed with 200 kg.dichlorethane and centrifuged at ,-2G C. Thereby are obtained 64 kg.mixture of dewaxed oil and solvent as well as 236 kg. mixture of solidwax hydrocarbons and enclosed therein fluid wax hydrocarbons withsolvent. From 64 kg. dewaxed oil and solvent, lli kg. eX- trac areobtained by distillation. The 236 kg. wax and solvent are now heatedunder stirring to from to +5 C. and are again subjected to continuouscentrifugation. There are thereby obtained 80 kg. petrolatum consistingof 38 kg. hard wax and 42 kg. dichlorethane, aswell as 1,56 kg. mixtureof fluid wax hydrocarbons containing -108 kg. dichlorethane and 48kg.oil. The latter is mixed with the originally obtained 14 kg. extract Asa final product there are obtained a total of 62% oil with a pour pointof -20 C. and a viscosity index of 86, and 38% wax having a meltingpoint of 66 C.

In ythe drawing, which is a diagrammatic View of an apparatus forcarrying out the above described example process: a is a tank forblending the distillate with the selective solvent; b, c, c, chillers; da centrifugal separator in which is separated the primary dewaxed oildissolved in a minor proportion of the solvent from the mixture of solidand fluid hydrocarbons (theprimary wax) and the bulk of the solvent; c astill for distilling off the solvent (whichA is returned to the solventstorage tank .f through line g) from the extract; h a heat exchangerwhereraising the pour Ain the temperature of the diluted primary wax israised, usually Vfrom 20 to 25 C., to obtain a mixture of solidcrystalline wax and a solution of fluid wax hydrocarbons and solvent, ithe centrifuge in which the solid crystalline wax and some of thesolvent are separated from the solution of uid parainicv oil and theremainder of the solvent; Ic the still in which the solvent is separatedfrom the said parafnic oil; m the still in which the solvent isseparated from the hard wax; n the return line for distilled solventfrom still k to the solvent storage tankconveniently through line Q1 othe return line for distilled solvent from still m to the solventstorage tank; and p aline through which a small proportion of thenon-parainic oil may be added to the oil to be dewaxed prior tochilling, as hereinafter described.

If the process is carried out in only one stage with the same quantityof the same solvent at for instance -|-5 C.. the major portion of thevaluable viscosity bearers, that is, those substances lthe viscosityindex.

which according to the method above described are obtained as extract inthe rst stage, remain in the said petrolatum owing to the unsatisfactoryselectivity at the temperature indicated. In this way not only a wax ofinferior quality is obtained but also a reduced yield of low quality oilhaving a pour point 0i +5" C. due to lack of extract substances by whichthe pour point is lowered.

It is true that it is possible to obtain a sufficient concentration ofextract substances in the dewaxed oil to ensure the desired pour pointby substantially increasing the amount of solvent, using in this case,for instance, a tenfold quantity, which can also be deduced by means ofthe laws of the solubility. However, the use of large amounts of solventnot only entails considerable economic disadvantages owing to the highre- Afrigerating and distilling energy utilized for the solvent, but aconsiderable dissolution of solid wax hydrocarbons also results, whichin turn raises the pour point of the oil considerably.

The selective effect of the dewaxing agents herein considered may alsobe utilized for obtaining substances which have the same qualities asthe so-called pour point reducers sold in the open market. It has beenfound, in connection with the dewaxing of (particularly) mixed base oilsor distillates with, for instance, dichloretnane, dichlorethylene,methylenechloride, trichlorethane, and less desirably,tetrachlorethylene and carbontetrachl-oride, and with mixtures of thesame with ketones, alcohols, `ethers, esters, etc. at low temperatures,for instance, below w20" C., that extracts are obtained of which smallamounts suice to reduce the pour point of oils 10 to 20 or more degrees,without having any practically unfavorable influence on the viscosityindex.

The lower the separating temperature used -for obtaining the naturalpour point reducer, the

lower the yield, but also the higher the concentration and consequentlythe effect.

If, for instance, a Roumanian overhead distillate is treated with thesame volume of dichlorethane at 30 C., about 15%l extract of highviscosity is obtained. If now only 3% extract is added to a gas oilhaving a pour point of +6 C. and a viscosity of 1.82 E. at 20 C. and aviscosity index of 90, the pour point ofthe gas oil is lowered to 12 C.,without changing If the same treatment of the overhead is carried out at40 C., it is true that only about 10% extract is obtained, but to obtainthe low pour point referred to above with the same gas oil it is nownecessary to add only 1%. With increasing amounts of extract the pourpoint is, of course, further lowered.

The amount of natural pour point reducer to be added is generally sosmall that a harmful iniiuence on the color of the oils treatedtherewith need not be feared. If necessary, the pour point reducer maybe made lighter in color by chemical or physical rening, for instance,with fullers earth in benzine solution yor the like.

vWhile the natural pour point reducers thus obtained have the sameeffect in regard to the lowering of the pour point and the maintenanceof the viscosity index as the articial ones which may be obtained, forinstance, by condensation of naphthalene, anthracene, etc., withchlorinated wax according to the method Friedl-Crafts, they offer thefollowing considerable advantages over the latter products.

, 1. They are natural products and therefore it is in many cases'unnecessary 'toadd 'a lforeign oiltoagivenoil. 'r i i' rlTheirrproduction is not dependent on special chemical and expensive reactionprocesses.

3. They can be obtained in more or less high hconcentration by usingsuitable selective solvents in connection with severaldewaxing'processes, and can then be addedto a parafinous oil as pourpoint reducer. Possibly they can -be obtained in comparatively lowconcentrationat the stage dewaxing according to the method describedabove; and after the division of the wax hydrocarbons into solid andfluid particles, they can again be added to the latter.

4. While the artici'al pour point reducers hardly influence the cloudpoint, the natural reducers cause a lowering of the same.

The natural pour point reducers may also beM obtained by firstliberating the oil at low tem-iA perature with the aid of anon-selective solventy from the crystalline hard wax, whereupon thetreatment with the selective agent is effected.

The natural pour point reducers produced acl.

cording to the process described above Imay be added to the oils to bedewaxed also prior to the chilling to low temperature or the removal ofthe wax, respectively, in order to obtain a better,v

the less it dissolves the paranic compounds on i the-other hand;naphtha, propane and similar light hydrocarbon oil fractions are notselective" solvents, as their temperature-solubility-curves forparaiflnic compounds do not essentially differ from theirtemperature-solubility-curves for non-parailnic compounds. The followingsolvents may be mentioned as examples of selective solvents: chlorinatedhydrocarbons, alcohols, ketones, aldehydes, esters and the like,separate or in mixtures, but of course the method is not restricted tothe use of these solvents and mixtures. However, it is to Ibe understoodthat by a selective solvent is meant to include only those solventswhose temperature-solubility curve for parafiinic compounds differs sosubstantially from their temperature-solubility curve for nonfparainiccompounds that they are relatively good solvents for the naphthenicand/or aromatic compounds and relatively poor solvents for theparaflinic compounds. Of such solvents, those whose sole or mainconstituent is a chlorinated hydrocarbon, of which a number of ex amplesare hereinbefore given, offer distinct advantages.

What I claim and desire to protect by Letters Patent is:

1. The process of treating wax-bearing hydro-y carbon oils to obtaintherefrom oils having low. pour points and good viscosity-temperaturecharacteristics, which comprises adding to the voil a solvent selectivenon-parainic hydrocarfbon and cooling to a temperature adapted to pre;-cipitate solid wax and iluid paraiinic hydrocarbons and centrifugallyseparating the sam'e with a major proportion of the solvent from the ofthe mixture of solid wax parainic hydrocarbons and solvent to form amixture of solid crys talline wax and a solution "of solvent andparafflnic oil and at that temperature separating the' last namedsolution, containing the major part of the solvent of said mixture, fromthe said solid crystalline wax and such minor part of the solvent as iscarried oiT with the wax.

2. The process set forth in claim 1 in which substantially all thesolvent present in the second specied `separating step is that which isadded thereto preparatory to the first specified separat' ing step.

3. The process set forth in 'claiml in which the said selective solventcomprises a chlorinated hydrocarbon.

4. The process set forth in claim 1 in which the temperature to whichthe solution is chilled preparatory to the specified centrifugalseparation is not substantially above 15 C. and in which the temperatureto'which the mixture of solid wax, paraiiinic hydrocarbons and solventIseparated inthe said centrifugal separation is heated preparatory to thesecond specified separation is not substantially less than 20 C. abovethe temperature to which it waschilled preparatory to the first speciedseparation.

5. The process set forth in claim l in which the temperature to whichthe` solution is chilled preparatory to the specified centrifugalseparation is not substantially above -15 C. and in which thetemperature to which the mixture of solid wax, parafnic hydrocarbons andsolvent separated in the said centrifugal separation is heatedpreparatory to the second specified separation is approximately 20-25"C. above the temperat'ure to which it was chilled preparatory to thefirst specified separation.

6. The process of treating wax-bearing hydrocarbon oils to' obtaintherefrom oils having low pour points and good viscosity-temperaturecharacteristics, which comprises adding to the oil a solvent selectivefor non-parafiinic hydrocar-bons and cooling to a temperature adapted toprecipitate solid wax and fluid parafnic hydrocarbons and centrifugallyseparating the same with a major proportion of the solvent from the oiland a. minor proportion oi" the solvent to thereby produce a solution ofa non-paralnic low pour-point, low cloud-point-reducing extract and aminor proportion of the solvent, subsequently substantially raising thetemperature of the mixture of solid wax parainic hydrocarbons andsolvent to form a mixture of solid crystalline wax and a solution ofsolvent and paraiiinic oil and at that temperature separating the lastnamed solution, containing the major part of the solvent of saidmixture, from the said solid crystalline wax and such minor part of thesolvent as is carried 01T with the wax, and adding said non-paranicextract in small proportions to said wax-bearing starting oil to therebyobtain a better crystallization of wax and increase the yield of oil.

7. The process of treating wax-bearing hydrocarbon oil to obtaintherefrom oils having low pour points and good viscosity-temperaturecharacteristics, which comprises adding to the waxbearing hydrocarbonoil a solvent selective for non-parainic hydrocarbons Vand cooling to atemperature adapted to precipitate solid wax enclosing therein fluidparafiinic hydrocarbons and subjecting the same to such centrifugaloperation as to separately discharge two constituents, namely, aconstituent which consists of a. solution of oil and solvent containingsuch minor proportion of the solvent that the oil in the solution isanon-parafnic low pour-point, low cloudpoint-reducing extract and aconstituentwhich is Va mixture of said solid wax and a solutioncomprising the remaining major proportion of the solvent and an oilwhich is a fluid mainly parainic oil, and subsequently substantiallyraising the temperature of said mixture to render a part of said solidWax fluid to thereby form a mixture'v ofsolid crystalline wax and asolution of solvent and oil which is mainly parainic and 10 tain thedesired product.

at that temperature separating the last named solution, containing themajor part of the s01- vent, lfrom the solid crystalline wax and suchminor part of the solvent as is retained with the wax.

8. The process set forth in claim '7, followed by separation of saidextract and said fluid mainly paraflinic oil from their respectivesolvents and mixing said extract and oil to thereby ob- BRUNO ENGEL-GERTIFI CA TE OF C ORREC TION Patent No. 2,948,159. May 9, 19h14.

y BRUNO ENGEL.

It is herebyr certified that error appears in theprinted specificationof the above numbered patent requiring correction asifollows: Page 5,first column, line 59, before "what I claimrl insert the followingparagraph --1 do not herein Claim the addition to the feed stock andsolvent blended therewith of a portion of the solvent extract, asthesame is included in the subject matter of a pending application filed byme November, 19h42, Serial No. i-hlhu;

and that the said Letters Patent should be read with thiscorrection-there.- in that the semeV may conform to the record of thecase in the Patent Office.

lsigned and sealed this 29th day of August, A. D. 19th.

Leslie Frazer (Seal) Acting Commissioner of Patents.

CERTIFICATE OF C ORRECTI ON Patent No. 2,5Ly8,u59. may 9, 191m.

BRUNO ENGEL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 5,first column, lines 65 and 66, claim 1 for the words "non-paraffinichydrocarbon read --for non-paraffinie hydrocarbons-H; and that the saidLetters Patent should be read with this correction therein that the samemay conform to the record of the .case in the Patent Office.

signed and sealed this 27th day of June, A. Demut.

Leslie Frazer (Seal) Y Acting` Commissioner Aof Patents

